Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a first image thereof.

FIG. 2 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a second image thereof.

FIG. 3 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a third image thereof.

FIG. 4 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a fourth image thereof.

FIG. 5 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a fifth image thereof.

FIG. 6 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a sixth image thereof.

FIG. 7 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a seventh image thereof.

FIG. 8 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting an eighth image thereof; and,

FIG. 9 is a front view of a display screen or portion thereof with a transitional graphical user interface, showing our new design and depicting a ninth image thereof.

The appearance of the transitional graphical user interface sequentially transitions forwards from FIGS. 1-9 and backwards from FIGS. 9-1. The process or period in which one image transitions to another image forms no part of the claimed design.

The broken lines illustrate the display screen or portion thereof and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a transitional graphical user interface, as shown and described. 